Does glycolysis require oxygen directly to be present? The answer is Yes or No.
Does glycolysis require oxygen?
The direct answer is no and the indirect answer is yes.
The glycolysis process truly does not require oxygen to proceed. The glycolysis process converts one molecule of glucose into two molecules of pyruvic acid in the absences of oxygens. Glycolysis takes place in virtually all living cells, including all animal cells, all plant cells, and almost all bacterial cells.
Since it does not need Oxygen and it occurs in approximately all living cells, it is suspected that the process had evolved in ancient times when there was no oxygen, in the atmosphere.
Although glycolysis does not require the presence of Oxygen, it does require an electron carrier molecule called NAD+ which receives an electron during the glycolytic pathway. NAD+ which is carrying an electron is called NADH.
In plant and animal cells, NADH provides an electron to the mitochondria to help produce ATP, thereby producing the energy. When mitochondria receive an electron, the NADH becomes NAD+ again. In this part when mitochondria produce ATP by receiving an electron from NADH, the glycolytic process requires Oxygen. That is, mitochondria can’t function without oxygen.
You know, plant and animal cells die without the presence of Oxygen. But why?
Without oxygen, mitochondria can’t function and NADH can not revert to NAD+. The regeneration NAD+ is essential for the glycolysis process. The glycolysis process cannot proceed without NAD+. Therefore in most cells, glycolysis indirectly requires Oxygen even though it does not need Oxygen in its process.
A few numbers of cells use a different mechanism to regenerate NAD+ from NADH. One method is, they undergo fermentation to regenerate NAD+ from NADH.
During the fermentation process in plant cells, they produce ethanol (the alcoholic drink) and carbon dioxide. Some microorganisms also perform fermentation process to produce alcohol, lactic acid, and carbon dioxide. In all types of fermentation, NAD+ is regenerated from NADH.
Some animal cells also revert NADH to NAD+ using a fermentation process. Thus they produce lactic acid, especially in human muscle cells.